Whites continued to decline as a share of the American population in 2009, and they now represent less than half of all 3-year-olds, according to a Brookings Institution analysis of census data released Monday.

The country’s young population is more diverse than ever, with whites now in the minority in nursery schools, preschools and kindergartens in eight states — Arizona, California, Florida, Hawaii, Mississippi, Nevada, New Mexico and Texas — and the District of Columbia, according to William H. Frey, a demographer at Brookings. That was up from six states in 2000.

“We are on our way to having a majority of minority students in U.S. schools,” Mr. Frey said.

Nationally, whites accounted for 58.8 percent of all school enrollment in 2009, Mr. Frey said, citing the new data, which measured enrollment from preschool to graduate school as of October 2009. That was down from 64.6 percent in 2000, a decline that came with falling birthrates as the white population aged.

Population growth has come instead from Hispanics, blacks and Asians, whose children represent ever larger shares of the school population. Twenty-three percent of children in kindergarten were Hispanic in 2009, up from 18 percent in 2000 and 10 percent in 1989. Hispanics now account for nearly a fifth of all enrollment from nursery school through college, Mr. Frey said.

The United States has been experiencing the biggest surge of immigrants since the late 19th and early 20th centuries, when European immigrants considerably expanded the population.

And while immigrants have long taken to cities, more recently they have spread throughout the nation, creating diverse student populations in places that had been overwhelmingly white.

The states whose white children dipped to below 50 percent of nursery school and kindergarten enrollment most recently were Arizona, Florida and Nevada, Mr. Frey said. Next in line are Georgia, Louisiana and Maryland, he said.

The increase in minority students in schools doesn’t mean our children are getting a better education yet. And the people who worry about these things are in no rush to change that.

The gap between the country’s diverse young population and its older white one is raising difficult issues for policy makers, who are trying to balance the growing costs associated with the aging white population with the need for financing to educate an increasingly diverse youth.

Education experts who have studied the issue say the United States is lagging behind in educating minority students. The past big wave of immigrants took more than a generation to integrate into the economy through education, they say, a delay the country can still afford in today’s age of global competitiveness.

“These students will be an important source of our labor-force growth as baby boomers begin retiring,” Mr. Frey said.